Mold forming apparatus



Patented June 13, 1933 PATENT- OFFICE GEORGE AMBUEHL, OF EVANSTON, ILLINOIS MOLD FORMING APPARATUS Application filed April 2, 1932. Serial No. 602,733.

My present invention relates to the provision of mold formin apparatus, or apparatus for facilitating the investment of patterns or models for the pur ose of providing a mold in which objects 0 the configuration of the patterns or models may be cast.

As will hereafter be seen, the facillties which I provide are peculiarly suitable for making molds for casting ob ects of small dimfinsions, such as crowns and inlays for teet The resent method, so far as I am aware, for mafiing molds for casting crowns and inlays consists in placing the pattern or model formed of wax or some other fusible or combustible material, upon a post or sprue, which sprue is supported 1n a 0 amber, and the investing material, consisting of plaster of Paris or some like material mixed with suflicient water so as to readily flow, is poured into the chamber and the plaster of Paris settles or avitates about the form or pattern and solidifies. After the solidification of the investment material and the suflicient drying thereof the post or sprue is withdrawn and the mold heated so as to drive off the fusible or combustible material of which the model or pattern is made through the channel left by the withdrawal of the post or sprue. The above described process of investing the-model and forming a mold requires care and experience in order to secure satisfactory results as more or less air remains associated with the particles of the in "estment material which sometimes accumula es to form voids in the mold and always ope tes to reduce the density of the mold even ere appreciable size voids are not producedtl Also the mixture of the investing material with the water is not always homogeneous, arid over-wet portions of the mold, when it is dried, also produce cavities or voids in the completedmolds.

As will hereafter be seen my apparatus secures molds of greater and more uniform density and operates to extract a considerable quantity of the water which woiild otherwise require to be dried out, thereby considerably shortening the time necessary in the forming of the molds. a

I had as my objects the provision of the facilities for conveniently and quickly investing models and patterns in forming molds for casting and the production of such molds of greater and more uniform densit I have attained the foregoing o jects by means of the apparatus illustrated in the accompanying drawing, in which- Fig. 1 is a vertical elevation, partially broken away, of a structure embodying my invention, and Fig. 2 is a horizontal section on line 2-2 of Fig. 1.

Similar reference characters refer to similar parts throughout the respective views.

As will hereafter be seen, it has been my objectto force the investment material intimately about the model or pattern by centrifuga action 'andfor this purpose I provide an electric motor 5 mounted vertically upon a suitable base or standard 6. The motor shaft 7 extends from the top of the motor and upon the top of the motor shaft is mounted a nearly cylindrical casing 11, the upper end of which casing is open. The bottom 8 of the cylindrical casing is preferably quite thick and is provided centrally with the recess or socket 9 for frictionally receiving and engaging the top of the motor shaft 7. The vertical walls of the casing 11 slightly converge as they rise from the bottom of the casing. and adjacent the bottom of the casing are provided through the vertical side walls opposite passageways 12. Upon the outside of the casing 11 so as to continue the passageways 12 are tubular embossments 13 having upon their ends enlargements or rims 14. Inside of the casing 11 the bottom walls thereof are curved spirally upwardly from lines extending opposite the leading edges of the passageways 12 to a line opposite the following edges of the opposite passageway so that the vertical edges 15 of the upwardly curved portions align with and constitute elongations of the following side walls of the passageways12 and constitute extensions and prolongations of the walls of the passageways 12.

I have stated that the beginning of the spirals are at the leading edges of the passageways 12 and that the termination of the spirals or the vertical edges 15 are located at battles to direct the investing mixture through the passageways 12. Fitting over the rims 14 and embossments 13 are hollow caps,16, the edges 17 whereof are thickened to fit behind the enlargements 14 and the closed ends of which caps are also preferably thickened in a slightly conical form, as at 18. The caps 16' are preferably made of a suitable grade of flexible and elastic vulcanized rubber. The post or sprue 19 upon which the model or pattern 20 is mounted is thrust through the apex of the conically thickened portions 18 of the ends of the caps, and it will now be seen that by providing such a conical thickening greater supporting power for the post or sprue 19 is secured and also a depression is formed in the mold about the channel provided by the withdrawal of the post or sprue 19, which facilitates the introduction of the fused metal into the mold.

When the aparatus is assembled, as above described and illustrated, the current is supplied to the motor which rotates the casing 11. The investin material, mixed with water so as to run reely, is then poured into the casing 11 and in a few minutes the motor is turned off and it will be found that more than half the water used in making the investment mixture may be poured, free from the investment material, from the casing and upon removing the molds from the rubber caps 16 they will be found to be appreciably more solid and compact than molds formed in the ordinary .way. By reason of the extraction of a considerable portion of the water, as above described, the final drying of the molds is much shortened.

It will also be found when a casting is made that the investing material has been brought more uniformly and intimately adjacent the surfaces of the pattern or model, as most minute configurations upon the surfaces of the patterns orv models are accurately reproduced.

Having described my invention what I claim as new and desire to secure by Letters Patent is:

1. An apparatus for investing a pattern or model comprising a casing disposed for rotation about its axis, means for rotatin said casing, detachable chambers formed 0% flexible and elastic rubber communicating with the interior of said casing carried radially by said casing, said detachable chambers affording means for supportitng a pattern or model therein.

2. An apparatus for securing the investment of a pattern or model comprising a casing disposed for rotation about its axis,

e porting a model or pattern within said chambers.

GEORGE AMBUEHL. 

